Re: ATM 10" Flex Mirror

[Dennis Woos <wooscons@sover.net>]

Charles,

Unfortunately, we did not take any pictures of the cell during
construction, and now that it is assembled there is not a lot to see.  I
can tell you that we followed Adler's design pretty closely.  We did add
a 1/2" Lexan ring between the collimation-pusher plate and the hard
rubber ring, and used only one neoprene ring.  We thought that this
would give us a little more clearance between the puller ring and the
collimation-pusher plate, and we were concerned that we might run out of
room to pull.  In fact, on our next project we will definitely provide
some way to gauge how much distance remains between the puller and
collimation-pusher.  A small hole in the collimation-pusher would work,
but maybe it is better to just mark the inside surfaces of the puller
and the collimation-pusher with black lines, so that the surfaces can be
clearly seen through the outside of the collimation-pusher plate and the
distance between them estimated.  On our 6", we don't know if we have
any pulling room left or not.

We are interested in truss constuction, especially since we hope to
build larger dobs in the years to come.  Maybe we should get familiar
with the truss construction techniques on the 10".  On the other hand,
we know how to build with sonotube, and we can probably finish sooner.
Maybe our final decision will depend on how much time we have left
before Stellafane!  In any case, we certainly appreciate all of the
info/advice we have received.

Dennis and Doug

CharlesMitchard@aol.com wrote:

> Hi Dennis,
> great to hear your flex mirror is performing so great.
> So many people have been trying to put me off building one that it
> great to hear of a positive result other than from the originators.
> My humble suggestion would be to go with a truss design,
> reasoning - my tube scope (steel)  is a real bitch to colimate so for
> the current project 8.75" f6 flex I designed the top end to use guitar
> machine heads to tension wire spiders. This gives me total control
> over the secondary mirror positioning in any axis you want and is very
> stiff with any vibrations dampening out very quickly. (or so it seems
> without using it yet)
> If your calculations of the focal length are slightly out then simply
> by altering the truss poles length you can change the secondary height
> etc.
> So far it does not seem any harder to build a truss than a standard
> dob, I've finished the base, alt/az bearings, mirror box (just a shelf
> really) and the top cage. just have to cut the poles to length when
> the mirror is finished.
> Dont forget - at star parties a truss looks cooler than a standard
> dob  ;-p
> Would love to see some pics of the flex cell if you have any.
> Charles